The role of the novel Fem protein VanK in vancomycin resistance in Streptomyces coelicolor
The role of the novel Fem protein VanK in vancomycin resistance in Streptomyces coelicolor
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DOI：
10.1074/jbc.m413801200
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发表时间：
2005-04-01
影响因子：
4.8
通讯作者：
Buttner, MJ
中科院分区：
文献类型：
--
作者：
Hong, HJ;Hutchings, MI;Buttner, MJ
非致病性、非糖肽产生放线菌天蓝色链霉菌携带一组7个基因（vanSRJKHAX），赋予对万古霉素的诱导型高水平抗性。vanK基因在先前表征的万古霉素耐药簇中没有对应物，然而vanK是S.天蓝色。VanK属于Fem酶家族，其将分支氨基酸添加到肽聚糖前体的茎五肽。在暴露于万古霉素时，VanRS双组分系统开启所有七种货车基因的表达，并且VanHAX酶重新编程细胞壁，使得前体终止D-Ala-D-乳酸（Lac）而不是D-Ala D- Ala，从而赋予对万古霉素的抗性，万古霉素仅结合含D-Ala-D-Ala的前体。在这里，我们提供了VanK是万古霉素抗性所需的生物化学和遗传学证据，因为在染色体上其他地方编码的组成型表达的FemX酶不能识别含有D-Lac的前体作为底物，而VanK可以。与该观点一致，携带Gly分支的含D-Lac的前体存在于瞬时暴露于万古霉素的野生型中，但在以相同方式处理的vanK突变体中检测不到。此外，femX无效突变体在万古霉素存在下是可行的，但在其不存在下死亡。因为只有VanK可以识别含D-Lac的前体，所以万古霉素诱导的VanHAX在vanK突变体中的表达是致命的，因此vanK是万古霉素抗性所需的。
The non-pathogenic, non-glycopeptide- producing actinomycete Streptomyces coelicolor carries a cluster of seven genes ( vanSRJKHAX) that confers inducible, high level resistance to vancomycin. The vanK gene has no counterpart in previously characterized vancomycin resistance clusters, yet vanK is required for vancomycin resistance in S. coelicolor. VanK belongs to the Fem family of enzymes, which add the branch amino acid( s) to the stem pentapeptide of peptidoglycan precursors. Upon exposure to vancomycin, the VanRS two- component system switches on expression of all seven van genes, and the VanHAX enzymes reprogram the cell wall such that precursors terminate D-Ala-D-lactate ( Lac) rather than D-AlaD- Ala, thus conferring resistance to vancomycin, which only binds D- Ala- D- Ala- containing precursors. Here we provide biochemical and genetic evidence that VanK is required for vancomycin resistance because the constitutively expressed FemX enzyme, encoded elsewhere on the chromosome, cannot recognize D- Lac-containing precursors as a substrate, whereas VanK can. Consistent with this view, D- Lac-containing precursors carrying the Gly branch are present in the wild type transiently exposed to vancomycin but are undetectable in a vanK mutant treated in the same way. Further, femX null mutants are viable in the presence of vancomycin but die in its absence. Because only VanK can recognize D- Lac-containing precursors, vancomycin- induced expression of VanHAX in a vanK mutant is lethal, and so vanK is required for vancomycin resistance.